Add cursed apple: a status-effect apple that inverts controls

Eating a cursed apple inverts the snake's steering for
CURSE_DURATION_TICKS ticks, shown on the top screen while active. The
sprite is a recolored copy of the rotten-apple tile since all existing
sprite tiles are already in use.

source/game_logic.cpp

@@ -89,6 +89,23 @@ bool check_collision_apples_rotten(GameState &state) {
     return true;
 }
 
+bool check_collision_apples_cursed(GameState &state) {
+    const std::array<int, 3> headpos = state.snake.front();
+
+    auto it = std::find_if(state.cursed_apples.begin(), state.cursed_apples.end(),
+                            [&](const std::array<int, 2> &apple) {
+                                return apple[0] == headpos[0] && apple[1] == headpos[1];
+                            });
+
+    if (it == state.cursed_apples.end()) {
+        return false;
+    }
+
+    state.cursed_apples.erase(it);
+    state.curseTicksRemaining = CURSE_DURATION_TICKS;
+    return true;
+}
+
 void spawn_apples(GameState &state) {
     if (state.apples.size() < 1) {
         std::array<int, 2> apple = { rand() % (X_MAX + 1), rand() % (Y_MAX + 1) };
@@ -102,3 +119,16 @@ void spawn_apples_rotten(GameState &state) {
         state.bad_apples.push_back(badApple);
     }
 }
+
+void spawn_apples_cursed(GameState &state) {
+    if (state.cursed_apples.empty() && (state.ticks % 20 == 0) && ((rand() % 5) == 0)) {
+        std::array<int, 2> cursedApple = { rand() % (X_MAX + 1), rand() % (Y_MAX + 1) };
+        state.cursed_apples.push_back(cursedApple);
+    }
+}
+
+void tick_status_effects(GameState &state) {
+    if (state.curseTicksRemaining > 0) {
+        state.curseTicksRemaining--;
+    }
+}